In a heating and air conditioning device of an automobile there are two air flow pathways. After the evaporator, air cooled by the evaporator can either flow via a cold air path directly to a mixing chamber or to outlets of the air conditioning device and thus past a heat exchanger, or flow via a warm air pathway first through the heat exchanger and then into the mixing chamber or to the outlets of the air conditioning device. In normal or comfort mode, air flow after the evaporator is divided between the cold air pathway on the one hand and the warm air pathway on the other hand, so that a mixed temperature is produced in the mixing chamber underneath the outlets of the heating and air conditioning device.
Mixing chambers are very small, owing to design space. An adequate mixing of cold and warm air will not occur in the mixing chambers, or will be insufficient, without supporting measures or installed parts such as ducts or air baffles, so that there may be excessively large temperature differences at individual outlets of the heating and air conditioning device. Maximum permissible temperature differences at individual outlets are specified by the car makers.
In order to control a temperature in the mixing chamber, a ratio of air quantities along the cold air pathway and the warm air pathway must be regulated. This is done with the aid of a temperature gate, which optionally blocks entirely one of the two pathways or block portions of a particular path by adjusting the gate position between end positions of the temperature gate. However, it may be necessary, due to limited design space, for the warm air path and the cold air path to be opened or closed by a separate gate. Yet the approach with two gates has the drawback that a quantity of warm air that flows into a warm air duct which is positioned at the end of the warm air path, at the entrance to the mixing chamber, or a quantity of cold air that flows into a cold air duct which is positioned at the end of the cold air path at the entrance to the mixing chamber, cannot be so well controlled as when only one temperature gate is installed, which opens up the entry cross section of a warm air duct, for example, in proportion to the gate travel.
In presently known devices, the use of two gates means that a temperature in a defrost outlet, for example, increases too fast at temperature gate positions “full cold” to “roughly 30/40% warm” and then hardly changes at all in temperature gate positions greater than 50%. Furthermore, a temperature in a ventilation outlet behaves opposite to that in the defrost outlet.
When cold air ducts are installed that are supposed to take cold air to outlets in a foot region, air quantity also cannot be controlled via the travel of the temperature gate. In the beginning, a temperature in the outlets of the foot region is reduced as desired, but for temperature gate positions greater than 50% this effect is no longer desirable. In this case as well, a control mechanism is lacking.
When conventional warm and cold air ducts are used, that is, ducts with inlet and outlet openings of any desired cross section and duct walls closed at the side, there are no control mechanisms for steering the air flow and thus, there are no mechanisms for controlling the function of the ducts as a function of the temperature gate position.
The problem which the invention proposes to solve consists in a control mechanism which enables better controlling of the function of warm and/or cold air ducts in a heating and air conditioning device.